<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

</body>

<script>
    var age = 30;
    alert(typeof age);//number

    var salary = 30000.05
    alert(typeof salary);//number

    /*String */
    var s1 = "11";
    var name = "zhangsan";
    alert(typeof s1);
    alert(typeof name);

    /*boolean true false*/
    var flag = true;
    var flag1 = false;
    alert(typeof flag);
    alert(typeof flag1);

    /*null */
    var obj = null;
    alert(typeof obj);//object

    /*undefined */
    var x;
    alert(typeof x);

</script>


</html>
